A distinct disadvantage hitherto known is that, using otherwise identical fiber stocks, yarns produced by prior art friction spinners have poorer physical qualities, such as tensile strength, than do yarns produced by rotor spinners.
Known friction spinners include those disclosed in U.S. Pat. Nos. 3,636,693 and 4,168,601, which we shall call class one friction spinners, U.S. Pat. No. 4,202,163, which we shall call class two friction spinners, and those as disclosed in U.S. Pat. No. 4,148,177 which we shall call class three friction spinners.
Class one friction spinners are characterized by the deposition of fibers on a roller with a perforated surface, the suction through which holds the fibers thereon, at a location at some distance from the yarn forming zone and are brought into the yarn formation zone adhering to that revolving perforate surface. Upon reaching the yarn formation zone, the fibers on the held surface have to be reoriented and twisted to form the yarn. Problems in forming yarn of desirable physical qualities have been encountered, due it is now believed to the difficulties in reorienting the staple fibers to provide the desired axial alignment for good yarn formation.
Class two spinners employ both rollers perforated and having air drawn thereinto, both rotating in the same direction or sense, clockwise or anticlockwise, and having discrete fibers fed directly into the yarn formation zone in the cusp space therebetween. Thus, while indeed at least one perforated roller rotates from without the cusp-space into the yarn formation zone and towards the zone of closest adjacency of the surfaces of the rolls, on the other hand at least one (the other) roller which is perforated rotates in the direction from the zone of closest adjacency of the surfaces through the zone of yarn formation and thence outwardly therefrom. Class two spinners are known to be commercially useful in yarn making, however, to the best of present knowledge such yarns so made suffer from the problems of somewhat poorer physical qualities as above indicated. Again, it is believed that the underlying problems relate to fiber twisting as acted upon by the two cylindrical surfaces rotating into and out of the yarn formation zone as well as by the suctional forces pulling antagonistically from both sides of the yarn formation zone at the surfaces of both rollers. Further, mechanical complexities concerning suction piping and the like, as well as the increased economic cost burdens involved in the need to move large volumes of air through the yarn formation zone to and through both rollers surfaces provide for other disadvantages.
The third class of spinners is intimated at but not described by U.S. Pat. No. 4,202,163, by the words, "It is also possible, however, to use the invention on spinning apparatuses which have only one air-permeable roller and an air suction unit disposed in it . . . ." Class three spinners are characterized by one perforated roller with air suction and another roller with no air suction, preferably an imperforate roller, and most preferrably by one with an irregular surface to permit better adhesion or frictional contact with the discrete fibers; all of the foregoing are disclosed in U.S. Pat. No. 4,148,177 aforementioned. Additionally, class three spinners are characterized by the rotation of both rollers in the same sense, and movement of the perforate roller from the zone of closest adjacency of the rollers' surfaces to and through the zone of yarn formation or cusp-zone, and thence away from the cusp-zone, and thus the movement of the imperforate roller into the cusp-zone of yarn formation towards the zone of closest adjacency of the rollers' surfaces. Here it is believed that again one does not obtain sufficient control over axial orientation of the fibers due to the frictional and suctional forces acting upon the fibers and their bundle being somewhat indeterminate, as is the twisting of the fibers into the bundle to produce the yarn. Up to the advent of this invention now to be defined, the art lacked the fullness of appreciation of the criticality of the interaction-combination of factors of how the discrete fibers are introduced into the cusp-zone, and how and of what type of axially parallel rollers are to be rotated in order to provide the desired degree of control over the fibers, how they are axially oriented relative one another and the fiber bundle formed, how they are twisted into the bundle in order to form a yarn of substantially improved physical qualities more nearly approaching that obtained by rotor spinners.